Coughs and Sneezes

If you think your cough or sneeze is no big deal, think again. Coughs and sneezes produce gas clouds that allow their germ-filled droplets to travel much farther than previously thought, according to a new study by Massachusetts Institute of Technology (MIT) researchers, published online in the Journal of Fluid Mechanics.

While you may see and feel the droplets of a cough or sneeze when someone fails to cover their mouth, the “multiphase turbulent buoyant cloud” of a sneeze—which propels individual droplets into long range—is invisible, said study author professor John Bush in an MIT News release. With allergy season underway, this gives you all the more reason to cover up that cough or sneeze to prevent the spread of your unwanted germs to others—both near and far away from you.

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Even more alarming is that the smaller droplets of a cough or sneeze may travel up to 200 times further if not part of a cloud, and may be capable of transmitting more infectious particles, according to MIT News. It was previously thought that droplets moved as groups of unconnected particles and that larger mucus droplets flew farther than smaller ones due to their momentum, researcher said.

“[The] Important role of the multiphase turbulent cloud [is] in enhancing the range of deposition of the small droplets and making the smaller droplets travel further away from the large droplets, and much further away than initially thought,” study author Lydia Bourouiba, an assistant professor in MIT's department of civil and environmental engineering, said in an interview with Healthline. “This is a change in the previous physical picture and highlights the potential for non-local transmission of diseases from room to room indoors.”

Inside the 'Turbulent' Cloud

To understand the patterns of transmission of respiratory infectious diseases, researchers used high-speed imaging and mathematical modeling to analyze coughs and sneezes.

“Direct observation of sneezing and coughing events reveals that such flows are multiphase turbulent buoyant clouds with suspended droplets of various sizes,” researchers wrote. “Our observations guide the development of an accompanying theoretical model of pathogen-bearing droplets interacting with a turbulent buoyant momentum puff.”

To predict the range of pathogens produced by this “turbulent buoyant” puff, researchers developed models of droplet fallout from the cloud. They found that “droplets remained suspended in the cloud until their settling speed matched that of the decelerating cloud,” they wrote.

Results of the study reveal that droplets 100 micrometers in diameter can travel five times farther than previously estimated, that droplets 10 micrometers in diameter can travel 200 times farther, and that “droplets less than 50 micrometers in size can remain airborne long enough to reach ceiling ventilation units,” according to MIT News.

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Reducing the Spread of Pathogens

“This study is the first step toward a more fundamental understanding of the physical mechanisms that play an important role in shaping the patterns of transmission in populations during outbreaks,” Bourouiba said in an interview with Healthline.

“The next steps include the investigation of the pathogen-load of the droplets and understanding (of) the mechanisms selecting their size and pathogen-load,” Bourouiba said. “This can all help target and improve mitigations strategies such as spacing between patients in hospitals, air ventilation and filtration in confined spaces.”

Guarding Yourself During Allergy Season

So you know about the “turbulent buoyant cloud” a cough or sneeze produces. Now what? Does this mean you have to wear a surgical mask to protect yourself during allergy season?

Carolyn Dean, MD, ND, Medical Advisory Board Member of the non-profit Nutritional Magnesium Association said that regularly washing your hands is actually the best way to avoid spreading germs.

“And don't rub your nose or put your hands in your mouth without washing your hands first,” Dean said in an interview with Healthline. 

If people are coughing near you, Dean suggests moving away. And if you have children or are sitting next to a child, ask them to “cover their mouths or nose when they cough or sneeze,” she said.

While Dean said allergies are not caused by germs, people who have allergies may be more prone to getting infected.

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“Avoidance of exposure to allergic triggers is the best allergy prevention,” Dean said. “This would be specific for each person, depending what they react to. You can prevent hay fever with good air cleaning systems. You can also take off shoes to avoid tracking in pollen and reduce sugar and dairy intake which causes thickening of mucus. If mucus is thin and flowing properly, it will trap pollens and then be sneezed out. If mucus is thick, the pollen attaches and begins its allergic cycle."

Drinking lots of water to help liquefy mucus can also help, Dean said, as well as taking extra vitamin C or stinging nettle herb.

In regard to the study, Dean said that wearing a surgical mask is “much too fear-inducing.”

"In studies where 100 people are exposed to cold or flu germs, only a few people succumb,” she said. “The focus of treatment for colds and flus should be on enhancing the health of the population so they don't get sick.”

“The best nutrient I know for boosting the immune system is magnesium,” Dean said. “It was found to be so powerful that in the 1920s in France, it was used as a treatment for viral polio. Taking magnesium every day can protect people from viral infection.”

However, not all forms of magnesium are equally absorbed in the body, Dean said. “Magnesium citrate powder mixed in hot or cold water is highly absorbable and can be sipped throughout the day,” she said.

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